/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.camunda.bpm.extension.reactor.projectreactor.selector;

import javax.annotation.Nullable;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A {@link Selector} implementation based on the given regular expression. Parses it into a {@link Pattern} for
 * efficient matching against keys.
 * <p/>
 * An example of creating a regex Selector would be:
 * <p/>
 * <code>Selectors.R("event([0-9]+)")</code>
 * <p/>
 * This would match keys like:
 * <p/>
 * <code>"event1"</code>, <code>"event23"</code>, or <code>"event9"</code>
 *
 * @author Jon Brisbin
 * @author Andy Wilkinson
 */
public class RegexSelector extends ObjectSelector<Object, Pattern> {

  private final HeaderResolver headerResolver = new HeaderResolver() {
    @Nullable
    @Override
    public Map<String, Object> resolve(Object key) {
      Matcher m = getObject().matcher(key.toString());
      if (!m.matches()) {
        return null;
      }
      int groups = m.groupCount();
      Map<String, Object> headers = new HashMap<String, Object>();
      for (int i = 1; i <= groups; i++) {
        String name = "group" + i;
        String value = m.group(i);
        headers.put(name, value);
      }
      return headers;
    }
  };

  /**
   * Create a {@link Selector} when the given regex pattern.
   *
   * @param pattern The regex String that will be compiled into a {@link Pattern}.
   */
  public RegexSelector(String pattern) {
    super(Pattern.compile(pattern));
  }

  /**
   * Creates a {@link Selector} based on the given regular expression.
   *
   * @param regex The regular expression to compile.
   * @return The new {@link Selector}.
   */
  public static Selector regexSelector(String regex) {
    return new RegexSelector(regex);
  }

  @Override
  public boolean matches(Object key) {
    return key instanceof String
      && getObject().matcher((String) key).matches();
  }

  @Override
  public HeaderResolver getHeaderResolver() {
    return headerResolver;
  }

}
